Supermodel Beverly Johnson brought a gunman to force a boyfriend to breakup with her, according to a lawsuit filed by the ex.

In documents filed in Riverside County, CA -- Mark Anthony Burk claims Beverly showed up at his home with an armed Chuck Zito, and a separation agreement.

Burk alleges Zito was flashing a gun during the January, 2008 incident -- while Beverly yelled at Burk to sign an agreement that would have paid him $2,000 to get out of her house, according to the papers.

Legendary "Godfather" producer Robert Evans is also being sued. As for why, Burk's lawyer tells TMZ he's alleging Evans -- who was once romantically involved with Johnson -- was involved in the scheme.

In the docs, Burk claims he escaped and hid at a neighbor's home until Beverly & co. left.

Burk also claims in the papers that Walter Morgan took personal belongings from Burk's home -- including his mother's ashes.

Burk is suing for emotional distress and unspecified damages.

UPDATE: Chuck Zito tells TMZ the day of the alleged incident Beverly Johnson hired him as a bodyguard. Chuck says, "I was not carrying a gun and don't need to carry one."